In Vitro Cysteine Reactivates Organophosphate Insecticide Dichlorvos-Inhibited Human Cholinesterases.

OBJECTIVES: Organophosphate (OP) pesticides inhibit both red blood cell (RBC) and plasma cholinesterases (ChEs). Oximes, especially pralidoxime (2-PAM), are widely used as antidotes to treat OP poisoning. In addition, N-acetylcysteine (NAC) is sometimes used as an adjuvant antidote. The current study aimed to assess the feasibility of using NAC as a single therapeutic agent for OP poisoning in comparison to in vitro 2-PAM. METHODS: This study was carried out at the Razi Drug Research Center of Iran University of Medical Sciences, Tehran, Iran, between April and September 2014. A total of 22 healthy human subjects were recruited and 8 mL citrated blood samples were drawn from each subject. Dichlorvos-inhibited blood samples were separately exposed to low and high doses (final concentrations of 300 and 600 µmol.L-1, respectively) of 2-PAM, NAC and cysteine. Plasma and RBCs were then separated by centrifugation and their ChE activity was measured using spectrophotometry. RESULTS: Although cysteine-and not NAC-increased the ChE activity of both plasma and RBCs over those of dichlorvos, it did not increase them over those of a high dose of 2-PAM. CONCLUSION: These results suggest that the direct reactions of 2-PAM and cysteine with dichlorvos and the reactivation of phosphorylated ChEs occurr via an associative stepwise addition-elimination process. High therapeutic blood concentrations of cysteine are needed for the elevation of ChE activity in plasma and RBCs; however, both this agent and NAC may still be effective in the reactivation of plasma and RBC ChEs.

Efficacy of fresh packed red blood transfusion in organophosphate poisoning.

The mortality rate caused by organophosphate (OP) poisoning is still high, even the standard treatment such as atropine and oxime improves a lot. To search for alternative therapies, this study was aimed to investigate the effects of packed red blood cell (RBC) transfusion in acute OP poisoning, and compare the therapeutic effects of RBCs at different storage times.Patients diagnosed with OP poisoning were included in this prospective study. Fresh RBCs (packed RBCs stored less than 10 days) and longer-storage RBCs (stored more than 10 days but less than 35 days) were randomly transfused or not into OP poisoning patients. Cholinesterase (ChE) levels in blood, atropine usage and durations, pralidoxime durations were measured.We found that both fresh and longer-storage RBCs (200-400 mL) significantly increased blood ChE levels 6 hours after transfusion, shortened the duration for ChE recovery and length of hospital stay, and reduced the usage of atropine and pralidoxime. In addition, fresh RBCs demonstrated stronger therapeutic effects than longer-storage RBCs.Packed RBCs might be an alternative approach in patients with OP poisoning, especially during early stages.

Can anisodamine be a potential substitute for high-dose atropine in cases of organophosphate poisoning?

A case of organophosphate (OP) poisoning was admitted to the emergency room. The patient accepted treatment with pralidoxime (PAM), atropine, and supporting therapy. It was observed that even after 22 h after treatment, 960 mg of atropine was not enough for the patient to be atropinized. However, a 160-mg follow-up treatment of anisodamine was quite enough for atropinization after 4 h. As a case report, more studies are required before any definite conclusion can be reached regarding the use of anisodamine as a potential substitute for high-dose atropine in cases of OP poisoning.

A comparison of tabun-inhibited rat brain acetylcholinesterase reactivation by three oximes (HI-6, obidoxime, and K048) in vivo detected by biochemical and histochemical techniques.

Tabun belongs to the most toxic nerve agents. Its mechanism of action is based on acetylcholinesterase (AChE) inhibition at the peripheral and central nervous systems. Therapeutic countermeasures comprise administration of atropine with cholinesterase reactivators able to reactivate the inhibited enzyme. Reactivation of AChE is determined mostly biochemically without specification of different brain structures. Histochemical determination allows a fine search for different structures but is performed mostly without quantitative evaluation. In rats intoxicated with tabun and treated with a combination of atropine and HI-6, obidoxime, or new oxime K048, AChE activities in different brain structures were determined using biochemical and quantitative histochemical methods. Inhibition of AChE following untreated tabun intoxication was different in the various brain structures, having the highest degree in the frontal cortex and reticular formation and lowest in the basal ganglia and substantia nigra. Treatment resulted in an increase of AChE activity detected by both methods. The highest increase was observed in the frontal cortex. This reactivation was increased in the order HI-6 < K048 < obidoxime; however, this order was not uniform for all brain parts studied. A correlation between AChE activity detected by histochemical and biochemical methods was demonstrated. The results suggest that for the mechanism of action of the nerve agent tabun, reactivation in various parts of the brain is not of the same physiological importance. AChE activity in the pontomedullar area and frontal cortex seems to be the most important for the therapeutic effect of the reactivators. HI-6 was not a good reactivator for the treatment of tabun intoxication.

Adjuncts and alternatives to oxime therapy in organophosphate poisoning--is there evidence of benefit in human poisoning? A review.

Organophosphate poisoning is common in developing countries. The morbidity and mortality with organophosphate poisoning is relatively high despite the use of atropine as specific antidotal therapy and oximes to reactivate acetylcholinesterase. Several adjunct and alternative therapies have been explored in animal and human studies. We reviewed the literature to ascertain if there was evidence of benefit of such therapies. Adjunct and alternative therapies included treatments to reduce poison absorption by topical application of creams, enhance toxin elimination by haemoperfusion or bioremediation and neutralise the poison by scavenging free organophosphate with cholinesterase-rich human plasma. In addition, magnesium, clonidine, diazepam, N-acetyl cysteine and adenosine receptor agonists have also been used to counteract poison effects. Detailed assessment was limited by the paucity of trials on adjunct/alternative therapies. The limited evidence from the review process suggested potential benefit from the use of human plasma infusion, early initiation of haemoperfusion and intravenous magnesium, in addition to standard therapy with atropine and pralidoxime. There appeared to be no additional benefit with alkalinisation or use of glycopyrrolate instead of atropine in human trials. Diazepam administration has been advocated by military authorities if symptoms developed following exposure to organophosphate. Bioremediation, clonidine, N-acetyl cysteine and adenosine receptor agonists have been evaluated only in animal models. The impact of adjunct and alternate therapies on outcomes in human poisoning needs to be further explored before implementation as standard treatment.

Comparison of effects of different antidotes on tabun-induced cognitive impairment in rats using water maze.

In the past, scientists focused on the development of antidotes (mainly anticholinergics in combination with reactivators of inhibited acetylcholinesterase-oximes) to increase the number of surviving nerve agent-intoxicated individuals. Recently, they are interested in antidotes able not only to protect nerve agent-poisoned men from lethal toxic effects but also to improve their life quality by improvement of their central cognitive functions. In our study, the water maze was used to measure spatial working learning and memory in the case of tabun-induced cognitive impairment in albino Wistar rats. Antidotal treatment consisted of atropine alone or a combination of atropine with an oxime (obidoxime, trimedoxime or oxime HI-6). Our results suggest that atropine alone is not sufficient as a treatment for saving cognitive functions impaired by tabun. On the other hand, the addition of oxime to atropine contributes to improvement of cognitive performance in tabun-poisoned rats regardless of type of oxime.

Evaluation of reactivation test in anaesthetized dogs with experimental intoxication with nerve agents.

Following repeated antidotal treatment of anaesthetized dogs (1 min with atropine, 10 min with atropine and obidoxime, 60 min with atropine and obidoxime) after the intoxication with soman, sarin and VX (1 x LD50, i.m.), the blood cholinesterases (erythrocyte, whole blood, plasma) were monitored and their reactivatability (whole blood) was determined. During this treatment, the activities of erythrocyte acetylcholinesterase (AChE), plasma butyrylcholinesterase (BuChE) and whole blood cholinesterases were monitored. Atropine and obidoxime did not affect cholinesterase activities in control animals, whereas administration of obidoxime to dogs intoxicated with nerve agent caused an increase in the cholinesterase activities. The sensitivity of cholinesterases decreased in the order erythrocyte AChE > whole blood cholinesterases > plasma BuChE, respectively. Following sarin intoxication, blood cholinesterases were increased after the obidoxime administration. Intoxication with VX showed a similar picture but reactivation after the obidoxime administration was greater. In soman intoxication, the picture of cholinesterase changes was similar during the first 30 min of treatment. Then the increase in AChE activity following obidoxime administration was not as high as in the case of sarin and VX intoxication. Thus, the reactivation efficacy of obidoxime during nerve agent intoxication indicates that its repeated administration could be easily monitored using the reactivation test.

Bispyridinium oximes as antidotal treatment of cyclosarin poisoning-in vitro and in vivo testing.

The mechanism of intoxication with organophosphorus compounds, including highly toxic nerve agents and less toxic pesticides, is based on the formation of irreversibly inhibited acetylcholinesterase, which causes cumulation of neuromediator acetylcholine in synaptic clefts and subsequent overstimulation of cholinergic receptors, that is followed by a generalized cholinergic crisis. Nerve agent poisoning is conventionally treated using a combination of a cholinolytic (atropine mostly) to counteract the accumulation of acetylcholine and acetylcholinesterase reactivators (pralidoxime or obidoxime) to reactivate inhibited acetylcholinesterase. In this study of cyclosarin poisoning treatment, oximes of different chemical structures (obidoxime, HI-6, BI-6, and HS-6) were tested in vitro on rat brain acetylcholinesterase (enzyme source: rat brain homogenate), and afterwards, they were tested in vivo in equimolar doses, in mice and rats. The HI-6 oxime appeared to be the most effective oxime in vitro and in vivo.

A case of aldicarb poisoning: a possible murder attempt.

A couple showing signs of cholinergic crisis was admitted to the hospital. Analyses with high-performance liquid chromatography and gas chromatography-mass spectrometry conducted on serum, urine, and stomach contents that were collected few hours after first symptoms showed the presence of aldicarb, which is the most potent carbamate insecticide on the market. A murder attempt was suspected because the patients showed the first signs some minutes after drinking coffee upon returning home and no commercial products containing aldicarb were found in the house. Because of the reversibility of inhibition of acetylcholinesterase, the patients recovered after treatment with atropine and toxogonin. They left the hospital after 12 days. To our knowledge, the serum concentrations of aldicarb reported in this paper are the highest reported for a nonfatal case.

[The mechanism of the effect of the cholinesterase reactivator diethyxime on different models of the development of delayed hypersensitivity in acute dichloroethane poisoning]. / Mekhanizm vliianiia reaktivatora kholinésterazy diétiksima na razlichnye modeli formirovaniia giperchuvstvitel'nosti zamedlennogo tipa pri ostroi intoksikatsii dikhlorétanom.

Formation of DTH to sheep red blood cells was studied in CBA mice on different models in acute DCE poisoning (0.75 LD50). The effect of the reactivator cholinesterase diethyxime on this reaction in acute poisoning, and the relation of the reactions under study in various experimental series with the activity of alpha-naphthyl-AS-acetatesterase in the spleen cells and popliteal lymph nodes were also studied. Acute DCE poisoning (0.75 LD50) lowered cellular immunity which was assessed according to DTH formation in various models due to decrease of alpha-naphthyl-AS-acetatesterase activity in the splenocytes and cells of the of the suppressor cells in the DTH reaction. The reaction was attended with decrease of alpha-naphthyl-AS-acetatesterase in the splenocytes of the donors and the popliteal lymph nodes of the recipients apparently due to relative prevalence in the spleen cells of T-suppressors which are distinguished by poor esterase activity. Diethyxime restored completely the formation of DTH studied in different models (with the exception of the reaction in which the effect of transfer of the suppressor cells was assessed) due to restoration of alpha-naphthyl-AS-acetatesterase activity in the cells of the lymphoid organs.

Cholinesterase status, pharmacokinetics and laboratory findings during obidoxime therapy in organophosphate poisoned patients.

1 The effectiveness of oxime therapy in organophosphate poisoning is still a matter of debate. It appears, however, that the often cited ineffectiveness of oximes may be due to inappropriate dosing. By virtue of in vitro findings and theoretical considerations we concluded in the preceding paper that oximes should preferably be administered by continuous infusion following an initial bolus dose for as long as reactivation of inhibited acetylcholinesterase (AChE) can be expected. This conclusion has called for a clinical trial to evaluate such oxime therapy on the basis of objective parameters. 2 Before transfer to the intensive care unit (ICU), 5 patients received primary care by an emergency physician. In the ICU, atropine sulphate was administered i.v. upon demand according to the endpoints: no bronchorrhoea, dry mucous membranes, no axillary sweating, heart rate of about 100/min. Obidoxime (Toxogonin) was given as an i.v. bolus (250 mg) followed by continuous infusion of 750 mg/24 h. 3 Intoxication and therapy were monitored by determining erythrocyte AChE (eryAChE) activity, reactivatability of the patient's eryAChE ex vivo, plasma cholinesterase activity, the presence of AChE inhibiting compounds, as well as the concentrations of obidoxime and atropine in plasma. 4 Obidoxime was effective in life-threatening parathion poisoning, in particular when the dose absorbed was comparably low. In mega-dose poisoning, net reactivation was not achieved until several days after ingestion, when the concentration of active poison in plasma had declined. Reactivatability in vivo lasted for a longer period than expected from in vitro experiments. 5 Obidoxime was quite ineffective in oxydemetonmethyl poisoning, when the time elapsed between ingestion and oxime therapy was longer than 1 day. When obidoxime was administered shortly after ingestion (1 h) reactivation was nearly complete. 6 Obidoxime levels of 10-20 microM were achieved by our regimen, and atropine could rapidly be reduced to approx. 20 microM, as attained by continuous infusion of 1 mg atropine sulphate/h. Maintenance of the desired plasma levels was not critical even when renal function deteriorated. 7 Signs of transiently impaired liver function were observed in patients who showed transient multiorgan failure. In the present stage of knowledge, we feel it advisable to keep the plasma concentration of obidoxime at 10-20 microM, although the full reactivating potential of obidoxime will not then be exploited. Still, the reactivation rate, with an apparent half-time of some 3 min, is twice that estimated for a tenfold higher pralidoxime concentration.

[The effect of acetylcysteine and dipyroxime on the immune reactions in acute dichloroethane poisoning]. / Vliianie atsetiltsisteina i dipiroksima na immunnye reaktsii pri ostroi intoksikatsii dikhlorétanom.

It was established in experiments on CBA mice and outbred rats that acute dichloroethane (0.75 LD50) intoxication leads to decrease of antiinfectious immunological and nonspecific resistance of the organism, antibody production, and cell immune response evaluated according to the delayed-type hypersensitivity (DTH) reaction. Administration of the antidote acetyl-cysteine increased suppression of the reactions under study (with the exception of DTH), while dipiroxim weakened it. The dipiroxim effects are associated with reactivation of immunocyte alpha-naphthyl-AS-acetatesterase by this compound (and possibly also of other types of esterases of immunocompetent cells).

Poststorage diastolic abnormalities of heart transplants: is vascular dysfunction or myocardial contracture the culprit?

BACKGROUND: Vascular dysfunction and myocardial contracture can both contribute to posttransplantation diastolic abnormalities commonly exhibited by heart transplants, but their respective importance remains incompletely elucidated. To address this issue, we assessed the effects of supplementing a new heart preservation solution, Celsior, with a nitric oxide precursor (L-arginine) and a compound known to uncouple excitation from contraction (2, 3-butanedione monoxime). METHODS: Fifty isolated buffer-perfused rat hearts were divided into four groups. In group 1, hearts were arrested with St. Thomas' Hospital solution No. 2 (Plegisol) and stored in normal saline solution. In group 2, Celsior solution was used for cardiac arrest and storage. Group 3 hearts were arrested with and stored in Celsior solution supplemented with 2 mmol/L of L-arginine. In group 4, Celsior solution used for arrest and storage was supplemented with both 2 mmol/L of L-arginine and 30 mmol/L of 2, 3-butanedione monoxime. All hearts were stored for 10 hours, subsequently reperfused for 1 hour on a Langendorff column, and left ventricular pressure-volume curves were constructed. 5-Hydroxytryptamine (10(-7) mol/L) and papaverine (5 x 10(-6) mol/L) were used to test changes in endothelium-dependent and endothelium-independent coronary vascular responses, respectively, and compared with those obtained during the preischemic period. RESULTS: After 10 hours of cold storage, a major postischemic contracture was found in group 1. Left ventricular diastolic function was best preserved in group 4 at the end of storage and over the entire period of reperfusion. Coronary vasodilatory response to 5-hydroxytryptamine was completely lost in all groups after cold storage and reperfusion. Endothelium-independent vasodilatory response to papaverine was preserved in 2, 3-butanedione monoxime-treated hearts, whereas it was reduced in other groups. CONCLUSIONS: Our results suggest that myocardial contracture plays a major role in posttransplantation diastolic abnormalities shown by cardiac allografts. Alleviation of contracture significantly improves the responsiveness of coronary smooth muscles but does not affect that of the vascular endothelium which needs to be handled by separate interventions.

[The therapeutic efficacy of alloxime in experimental carbamate pesticide poisoning]. / Terapevticheskaia éffektivnost' alloksima pri éksperimental'noi intoksikatsii karbaminovymi pestitsidami.

The new cholinesterase reactivator alloxime, 10 mg/kg, shows a marked therapeutical benefits in acute intoxication rats with carbamine pesticides such as carbofuran, pirimor, elocron. The therapy of alloxime in combination with atropine, 10 mg/kg, results to their combined therapeutical effect, the toxicity of carbofuran, elocron, and pirimor (by LD50) decreasing by 8.4, 5.6, and 3.5 times, respectively). The mechanism of alloxime's therapeutical action is due to its capacity to restore cholinesterase activity in the central nervous system, normalizing neuromuscular transmission and hepatic and renal cytochrome P-450 levels.

Improvement of motor function in multiple sclerosis by use of protopam chloride.

PAM, a cholinesterase reactivator, was administered orally and parenterally to 37 patients with multiple sclerosis and a control group of 24 patients with other neurological diseases and pain syndromes. The effects of the administration of this compound in these patients with and without electrical stimulation of the spinal cord were studied. The clinical response to the drug follows a known time course and is dose related. Administration of large doses orally or intravenously aggravates existing neurological dysfunction. With a dose of 1,000 mg intravenously, a characteristic response is the temporary appearance of new ophthalmological abnormalities, followed by significant improvement in motor control and behavior, which gradually subsides. Parenteral administration is superior to oral. Tolerance to the drug is observed. The presence of electrical stimulation of the spinal cord complements the action of the drug. When electrical stimulation is withdrawn, the effect of the drug reproduces the effect of the electrical stimulation. It is suggested there is a defect in cholinesterase in multiple sclerosis patients, and its reactivation may have a significant relationship to signs and symptoms.

[Experimental studies on the efficacy of PAM against sumithion poisoning].

The efficacy of 2-Pyridine aldoximide methiodide (PAM) for lethal acute poisoning by fenitrothion (FNT) was investigated in mice and dogs. Sumithion (FNT 51.7%, emulsifiers 12.5% and xylol 35.8%) was used as fenitrothion. 1. FNT at 1500 mg/kg was administered orally to mice. After ten minutes 50 mg/kg of PAM was injected once iv, and plasma, erythrocyte, brain, liver and kidney ChE activities were investigated 30 and 60 min later. Recovery in ChE activity was found in every organ but the brain at 30 min, but no efficacy of PAM was observed at 60 min. 2. After administering 1500 mg/kg of FNT orally to mice, the life-saving effect was studied from the changes in mortality due to variation of PAM route, dosage and number of administrations. With oral administration of 1500 mg/kg of FNT, 75 to 85% of the animals died. The mortality ranged from 80 to 95% when the animals received a single intravenous injection of 50 mg/kg of PAM between zero and 60 min following the FNT administration. Thus, a single intravenous administration of PAM at 50 mg/kg showed no life-saving effect on the animals given FNT. However, the mortality was reduced to 45% when the animals received repeated subcutaneous injections of 20 mg/kg of PAM at a 3-hr interval from just after administration of FNT over 24-hr. In other repeated subcutaneous injection experiments, the mortality ranged from about 55 to 65%. In any PAM-treated group, the survival time was prolonged. This life-prolonging effect was more marked in the case of repeated subcutaneous injections of PAM by 12-hr and even more by 24-hr, than in the case of a single intravenous injection. FNT treatment caused marked salivation and watery diarrhea, and PAM clearly inhibited these signs of the muscarinic action of FNT. There was a high relationship between this inhibitory effect of PAM on the muscarinic action and its life-prolonging or life-saving effect. 3. PAM (150 mg/animal/shot, iv) was given 12 or 13 times during 7 hr from 10 min (4 animals), 3 hr (1 animal) and 6 hr (2 animals) after administration of FNT at 150 mg/kg. The effects of PAM on survival, plasma ChE activity, plasma protein (TP) and hematocrit (Ht) values were examined. The 3 dogs given FNT alone all died within 53 hr of administration, whereas 6 out of 7 animals treated with PAM survived.(ABSTRACT TRUNCATED AT 400 WORDS)

[Therapeutic effectiveness of diethyxime in poisoning by anticholinesterase-action carbamate pesticides]. / Terapevticheskaia éffektivnost' dietiksima pri otravlenii karbaminovymi pestitsidami antikholinésteraznogo deistviia.

Unlike dipyroxime (10 mg/kg), a new cholinesterase reactivator diethyxime (20 mg/kg) exerts a therapeutic action in acute poisoning of rats with carbamine pesticides (carbofuran, elocron, pirimor, croneton). Therapy with diethyxime combined with atropine (at a rate of 10 mg/kg) leads to the summation of therapeutic effects. At the same time the toxicity of carbofuran, pirimor, croneton and elocron as regards the LD50 decreases 8.75-fold, 5.4-, 4- and 2,84-fold, respectively. The mechanism of the therapeutic action of diethyxime is determined by its capacity to recover cholinesterase activity both in the peripheral and central nervous systems, as well as to normalize neuromuscular transmission. It is necessary to take into account the cholinolytic effect displayed by diethyxime.

[Use of acetylcholinesterase reactivators and central cholinolytics in the treatment of experimental tetanus poisoning]. / Primenenie reaktivatorov atsetilkholinésterazy i tsentral'nykh kholinolitikov pri lechenii éksperimental'noi stolbniachnoi intoksikatsii.

Experiments were conducted on rabbits with tetanus intoxication induced by the intravenous injection of a lethal dose of the toxin; a study was made of the therapeutic efficacy of the acetylcholinesterase reactivators--dipyroxim and isonitrosine, and also of the central cholinolytics--amizyl and diphacyl. In dose of 25 mg/kg dipyroxim produced no therapeutic effect, and in doses of 30--40 mg/kg caused the animal death. Amizyl and diphacil in a dose of 3--4 mg/kg caused elimination of tonic convulsions for 1 1/2--2 hours. As to isonitrosin--it produced the same effect for 4--5 hours. In case of combined administration of reactivators and cholinolytics convulsions were eliminated for 4--5 hours.